Forces (terminal velocity, moments, elasticity) Flashcards
What do resultant forces cause (2)
Change in shape
Change in their motion
What does an object that is not changing motion or shape experience
No resultant force
What are forces so what do they have
Vectors, so have a magnitude (size e.g. 10 newtons) and a direction
What are scalers
Not vectors, they are quantities that only have a magnitude e.g. length, area, mass, time
What must you look at to find the resultant force
Size and direction
What is Newton’s first law
If the resultant force acts on an object then that object will accelerate
So if there are a number of forces on an object but the resultant force is 0N then there will be no change in motion
What is Newton’s second law
Resultant force = mass x acceleration
F = m x a
What happens if the resultant force is in the direction of motion in an object
It will accelerate
What happens if the resultant force is opposing the motion of an object
It will decelerate
What does friction oppose
Motion
What is the equation that links gravitational pull, weight and mass
w = m x g
What is terminal velocity
The maximum constant speed of an object as the resistance is preventing it from accelerating any further
How does an object reach its terminal velocity
As an object falls it accelerates
As the object falls and gets faster the resistive force increases
Acceleration starts to decrease as the resultant force is getting less
At a certain speed the resistance and the weight will eventually be equal so the forces are balanced and the object is no longer accelerating
The object continues to fall but at a constant speed which is called its terminal velocity
How can we increase the terminal velocity
Make the object more aerodynamic or streamlined so resistance is reduced
What is a moment
It is the turning effect caused by a force
What is a pivot point
A point which the object can turn about when a force is applied
When are bigger moments created (2)
The force causing the effect is larger
The perpendicular distance from the pivot point is increased
What is the equation for moments
Moment = force x perpendicular distance
What are moments
Vectors, they have a magnitude and a direction
What causes the direction of movement during a moment
The direction of the turning effect
What is the principle of moments
The object is balanced (in equilibrium) so all the anti-clockwise moments added together are equal to all the clockwise moments added together
What is the centre of mass
The point at which all the mass of an object appears to be
What determines the stability of an object (2)
The centre of gravity
The length of base
What is stability
It is the measure of how far an object can be displaced from its resting position and still return when released instead of toppling
When will an object return back to its resting position
When the weight arrow falls within the case as it will experience an anti-clockwise moment
When will an object topple over
When the weight arrow is past the base so it experiences a clockwise moment
What is an elastic material
If a material returns to its original shape once a deforming force is removed it is said to be elastic
What is a plastic material
If a material is permanently deformed when a force is applied it is plastic
What is Hooke’s Law
When the extension of an object is directly proportional to the force applied to it
How do we calculate the applied force
w = m x g
How do we calculate extension
Total new length - original length
What is the equation for Hooke’s Law
Force is directly proportional to extension F 🐟 x
F = kx
F means force
k means the constant, so how stiff the material is (how much force for a certain extension)
x means is the extension
Why is a rubber band not obey Hooke’s law
The force and extension are not directly proportional as the lines on the graph are not straight
